Annealing furnace



Patented June 11, 1929.

UNITED STATES PATENT OFFICE.

WILLIAM M. HEPBURN AND ERNEST W'. WEAVER, OF TOLEDO, OHIO, ASSIGNORS TO THE SURFACE COMBUSTION COMPANY, INC, OF TOLEDO, OHIO, A CORPORATION OF NEW YORK.

ANNEALING' FURNACE.

Application filed February 8, 1928. Serial No. 252,719.

This invention relates to improvements in annealing furnaces and more particularly to annealing furnaces through which strands of wire may be continuously passed while being annealed.

In the conventional type of -ealing furnace of the direct fired type, the fuel employed for heating the furnace must be of such character that the heating gases or products of combustion will not have adeleterious effect on the wire. Not only must the fuel be such as to enable a neutral furnace atmosphere to be maintained in order to prevent scaling of the wire but the gases or products of combustion themselves must not contain such products 'as would corrode the wire. The most satisfactory fuels meeting these requirements are clean gas and electricity, both of which .are relatively expensive. While the wire is being brought up to its critical temperature from a cold state a relatively great amount of heat is required and during that period it is' not particularly sensitive to corrosion by furnace gases. After the wire has been brought up to heat it does not require very much heat to hold it at a given temperature during its soaking period.

This invention has for its object to provide a continuous wire annealing furnace whegein the wire during its heating-up period may be heated by a relative] inexpensive fuel, or in other words, a fue which while perfectly satisfactory where the character of the products of combustion is of minor or no im ortance, is not satisfactory for use where clhse control of the character of the furnaceatmosphere and temperature is necessary. Such fuels are coal, oil, producer gas, etc.

The cheaper fuels usually contain sulphur which when the steel or wire is hot causes objectionable effects on the product and, therefore, are not satisfactory for use where a wire having a smooth, clean surface is re quired and where but a single heating chamber is provided.

In accordance with this invention, the anhealing furnace is provided with two directfired heating compartments or chambers which are in restricted communication with each other. The first, or main heating compartment, wherein the wire is brought up to or near its critical temperature is in accordance with this invention designed to be heatthe front end of the main heating chamber.-

The main heating chamber at its front end is provided with a. preliminary heating chamber through which the hot products of combustion from the main heating, chamber flow in order to preliminarily heat the .Wire.

For a further understanding of the invention reference is made to the detailed descript-ion, taken in connection with the accompanying drawing forming part of the specification.

Referring to the drawing Figs. 1 and 2 taken together constitute a longitudinal vertical section through the im roved furnace, Fig.2 being an elongation of the right hand end of the furnace shown 'in Fig. 1. Fig. 3 is zhvertical sectional view taken on line 33' of F ig. 1. Fig. 4 is a vertical sectional view taken on line 44 'of Fig. 1.

In the drawing, letter A. indicates the preliminary heating chamber, B the main heating chamber and C the soaking chamber. Rising upwardly from the discharge end of the preliminary heating chamber A is an upright wall 10, which constitutes the front wall of the main heating chamber B. The roof 12 of the main heating chamber slopes downwardly towards the floor or hearth 14: of the furnace and finally straightforward as at 16, until it meets the wall 18, which separates the main heating chamber B from the soaking chamber G.- Communication is had between the two chambers B and C by way of a restricted passageway 20 between the hearth of the furnace and the foot of the wall 18.

At the front end of the heating chamber B is a transversely extending wall or arch 22 of substantial length, the front of this arch being spaced from the dischar e end of the preliminary heating chamber in order to rovide a port or passage 24 for reasons hereinafter more full Y set forth. Firing through the front we! 10 of main chamber entire length of the.. furnace.

B is an oil burner enerally indicated at 26. The flame from the oil burner passes between the inclined roof 12 and the top of the arch 22 towards the wall 18 at thefar end ofthe main heating chamber. The products of combustion from the oil burner do:

not enter the soaking chamber C but after impinging against the wall l8 flow backwardly beneath the arch 22 on their way to the outlet 28 in the top of the preliminary heating chamber A. Connecting with the waste gas outlet 28 is a recuperator generally indicated at 30 through which the produ ts of-combustion pass. 32 indicates a pipe through which air is supplied to the recuperator for heating. and 34 the pipe through which the heated air flows fromthe recuperator to the oil burner 26. y

In accordance with this invention some of the products of combustion are recirculated within the heating chamber B, some of the the flame from the oil burner and tends to more effectually direct the hot products of combustion back to the preliminary heating chamber A on their way to the outlet 28. The wire is entered throu h the door 36 at the front end of the cham er A and is continually passed through the furnace.

The soaking chamber O .is a relatively long, shallow .chamber and in accordance with the present showing is provided with a series of gas burners 38, which project through the side walls of the furnace. The floo'r, or hearth, of the soaking chamber C is a continuation of the floor or hearth-14 in the main heating chamber B, this hearth extending in a common level throughout the The wire-V rests on the hearth 14 throughout its passage throu h the furnace. By reason of the fact that t e wire is passed through the furnace in individual strands the communicating passage 20 between the main chamber B and the soaking chamber C can be made relatively shallow. The wire may for practical purposes be considered as substantially filling the space 20 and, therefore, the passage of combustion products from .the'chamber B into the chamber O is effectually prevented. Openings 39 in the roof of the soaking chamber provide .for the exit of products of combustion therefrom, movable tiles 40 being disposed over the openings 39 to regulate the amount of gases discharged at any given point in the length of the chamber as will be readily understood. Other normally covered openings 41 are provided for the insertion of pyrometers. At the discharge end of the soaking chamber is a door 42 which like the door 36 at the front of the furnace may be elevated at sufiicient distance to allow the wire to pass out of the furnace. .Any suitable mechanism generally indicated at 44 controls the opening and closing of the doors. i

The mode of operation ofthe furnace will be readily apparent from the preceding description. The wire is entered in the preliminary heating chamber A and is heated by the products of combustion which flow thereinto from the main heating chamber B] As the wire continues to progress through the main heating chamber B it will, of course, absorb more and more heat until its final heating temperature is approached. \Vhen the wire reaches a temperature say between 1300 F. and 1600 F. it will be just about ready to pass under the foot of the wall 20 which divides or separates the chamber B from th e.cham ber O. \Vhile at this temperature the wire is hot enough to be oxidized by the gases resulting from the burning of the fuel oil, nevertheless the wire will be retained in the chamber B for such a short period of time while at that temperature that very little or substantially no oxidation takes place. It is, of course, preferred that the wire shall be ready to pass into the soaking "chamber at or about at the attainment of its critical temperature in order to avoid any possible oxidation of the wire. .Upon the wire arriving in the soaking chamber O the balance of the heat is furnished by the gas burners which fire into the soaking chamber O. As already pointed out these gas burners will utilize clean gas -in order that the character of the furnace atmosphere in the chamber C may be readily controlled. been heated up to or at near its critical temperature very little heat will be required to maintain the wire at the desired temperature during its soaking period.

By heating the main chamber B by a relatively inexpensive fuel, like fuel oil, and reserving the use of the more expensive fuel for soaking chamber, the annealing operation can be carried on at considerably less expense than would be the case if the expensive fuel were utilized for the firing of the entire furnace. \Vhile we have shown the soaking chamber as providedwith gas burners it willbe understood that it is within the scope of the invention to heat the soaking chamber by .means of electricity. In-fact, any suitable fuel may be used for firing the soaking chamber so long as the fuel does not produce deleterious products of combustion, which would tend to oxidize the wire while in its heated state. In order to more efi'ectually prevent infiltration of deleterious On account of the wire having gases from the main firing chamber B into the soaking chamber C an internal furnace pressure in excess of that in the main heat ing chamber will be maintained in the soaking chamber C in any suitable manner.

What is claimed is:

1. A continuous annealing furnace comprising main and final heating chambers arranged end to end, a restricted work passage 'therebetween, a burner firing into the main chamber from its front end in a direction toward the final heating chamber, a preheating chamber opening on the main chamber, and Waste gas outlet in the preheating chamber through'which the products of combustion from the main chamber must pass in passing out of the main chamber, and means for heat-ing the final heating chamber.

2. A continuous annealing furnace comprising direct-fired main and final heating chambers arranged end to end, a restricted work passage therebetween, an arch in the main chamber beneath which the work passes, a burner firing into the main chamber below the roof thereof and above said arch in a direction toward the final heating chamber, means for heating the final chamber, a preheating chamber through which the work passes before reaching the main chamber,

an outlet in the preheating chamber for products of combustion ,formed in the main chamber, and a port at the front of said arch through which products of combustion may be induced to flow upwardly from therebeneath by the fresh incoming fuel for recirculation in the main chamber.

3. In combination, a heating chamber, a Wall extendingtransversely of the chamber between the roof and hearth thereof, a burner firing into the chamber from one end between the said wall and roof said wall beginning at a point in advance of-the burner and terminating intermediate the ends of the chamber, whereby combustion products after entering the chamber beyond the far terminal of said wall may return beneath the wall and pass upwardly at the front end thereof for recirculation with the stream of 'com bu stibles leaving the burner, a preheating chamber opening on said heating chamher at the burner end thereof the hearths of both chambers being in alinement, and an exit for spent combustion gases in the preheating chamber.

In testimony whereof we herebyv afiix our signatures.

WILLIAM M. HEPBURN. ERNEST W; WEAVER. 

